This application claims the priority of German Patent Document 199 19 975.2, filed Apr. 30, 1999, the disclosure of which is expressly incorporated by reference herein.
The invention relates to an air-conditioning system for a passenger cell of a vehicle of the type comprising:
an evaporator arrangement in an air stream,
a heat exchanger for heating the air stream, said heat exchanger being arranged downstream of the evaporator and having a heating medium flowing through it permanently,
at least one air-mixing space which is directly adjacent to an air outlet side of the heat exchanger and which has a warm-air inlet covering at least part of an air outlet surface of the heat exchanger and a cold-air inlet forming a mouth of a cold-air duct bypassing the heat exchanger,
a warm-air control member setting the opening cross section of the warm-air inlet and
a cold-air control member setting the opening cross section of the cold-air inlet.
A known air-conditioning system of this type (German Patent Document DE 197 50 381 A1) regulated on the air side or free of any heating valve has a heat exchanger which extends in the vertical direction of the vehicle and over the top side of which the cold-air duct is led to the air-mixing space. In this type of air-conditioning system, because a controlled valve in the circuit of the heating medium is dispensed with, heating medium circulates through the heat exchanger even when the xe2x80x9cmaximum coolingxe2x80x9d operating mode, in which the passenger cell is to be supplied with maximum cooling air, is switched on. For the purpose of a compact design of the air-conditioning system, the evaporator and heat exchanger are arranged closely adjacent to one another, and, for reasons of space, the air-mixing flaps for the supply of warm air and cold air are shifted into the air-mixing space, the warm-air flaps consequently being arranged on the air outlet side of the heat exchanger. In the xe2x80x9cmaximum coolingxe2x80x9d operating mode, therefore, the cold-air stream which flows along the heat exchanger front side facing the evaporator and enters the cold-air duct is unavoidably heated by the heat radiation from the heat exchanger.
In order to reduce this heating, in the known air-conditioning system mentioned above an umbrella-like or diaphragm-like guide is provided, which, starting from the upper end of the heat exchanger, projects downwards and diagonally in the direction of the evaporator on the front side of the heat exchanger. This umbrella-like guide prevents the air heated in the heat exchanger from rising and passing into the cold-air duct.
An object on which the invention is based is to improve an air-conditioning system of the type mentioned in the introduction in terms of a further reduction in cold-air heating in the xe2x80x9cmaximum coolingxe2x80x9d operating mode.
The object is achieved according to the invention, by providing an arrangement of the above-noted type wherein an air-guide flap pivotable into two pivoting end positions is arranged at an inlet of the cold-air duct on the air inlet side of the heat exchanger facing the evaporator, in such a way that, in a first pivoting end position assumed in a xe2x80x9cmaximum coolingxe2x80x9d operating mode, the air-guide flap covers only a part region of the air inlet surface of the heat exchanger and assumes an orientation in which it diverts the air stream towards the inlet of the cold-air duct.
The advantage of the air-conditioning system according to the invention is that, in the xe2x80x9cmaximum coolingxe2x80x9d operating mode, the air inlet surface of the heat exchanger through which the heating medium flows is partially covered by the pivotable air-guide flap on the heat exchanger front side or cold-air side facing the evaporator, as a result of which, in conjunction with the closed warm-air control member on the air outlet side of the heat exchanger, a build-up of air is formed in the heat exchanger and assists the air-guide function of the air-guide flap arising due to the orientation of the latter, specifically the function of guiding the cold-air stream directly to the inlet of the cold-air duct. At the same time, the orientation of the air-guide flap prevents parts of the air cushion formed by this air build-up from being entrained by the cold-air stream and the air in the air cushion from being exchanged. The heating of the cold air by means of the heat exchanger is consequently reduced to a minimum. In the xe2x80x9cmaximum heatingxe2x80x9d operating mode, the air-guide flap is pivoted away from the heat exchanger into the inlet region of the cold-air duct, so that the maximum air inlet surface of the heat exchanger is available unrestrictedly for the passage of air.
Advantageous embodiments of the air-conditioning system according to the invention, along with expedient developments and refinements of the invention, are specified herein and in the claims.
According to an advantageous embodiment of the invention, the air-guide flap, when in its second pivoting end position assumed in the xe2x80x9cmaximum heatingxe2x80x9d operating mode, at least partially covers the inlet region of the cold-air duct and assumes an orientation in which it diverts the air stream towards the air inlet surface of the heat exchanger. This outward pivoting and orientation of the air-guide flap contributes, in the xe2x80x9cmaximum heatingxe2x80x9d operating mode, to an improved air flow within the heat exchanger region adjacent to the cold-air duct and reduces the flow resistances at the heat exchanger inlet.